1. Field
Example embodiments relate to an organic/inorganic composite compound for fouling resistance, a membrane including the same for fouling resistance, and a method of preparing a membrane for fouling resistance.
2. Description of the Related Art
Membrane fouling is an important problem in the membrane industry. Membrane fouling is characterized by a decrease in membrane permeation rate over time, which is generally induced by components in a feed solution passing through the membrane. The decrease may be caused by molecule adsorption in the membrane pores, pore blocking, and/or cake formation on the membrane surface. A decrease in permeation rate increases operation energy use, and to overcome this, cleaning is required. However, cleaning is only a temporary solution, and fouling typically decreases the life-span of the membrane.
As a method for reducing fouling of membranes for reverse osmotic pressure (RO), forward osmotic pressure (FO), ultrafiltration (UF), and microfiltration (MF), the impartation of a hydrophilic surface to the membrane is a solution that is capable of providing fouling resistance while increasing the life-span of the membrane.
To increase fouling resistance of a membrane by graft polymerization of a hydrophilic group on the membrane surface, various hydrophilic monomers are grafted by various synthesis membranes to restrict fouling by microorganisms such as bacteria and the like and natural organic materials such as proteins and the like. A drawback of the surface modification method is that the initiation of graft polymerization uses relatively high energy gamma radiation or plasma. This approach may increase membrane manufacture cost and may also be relatively difficult to control.
Another method for producing a fouling resistant surface is to manufacture a membrane including a microphase-separated polyacrylonitrile amphiphilic graft copolymer. Although there are drawbacks that a novel material should be developed through synthesis and a membrane manufacturing method should be established to manufacture a separation membrane, this method may minimize transformation of the membrane and provide relatively long-term stability.
Another method for producing a membrane for fouling resistance is to introduce polymeric additives having hydrophilicity during manufacture of a membrane. Since this method does not require a processing step in the manufacture of a membrane, the cost may be lower, and it may be incorporated into the existing membrane casting process with relative ease. To obtain uniform pore size, relatively homogeneous polymers should be used. However, in this system, the presence of strong chemical bonding may only occur infrequently, and thus, the hydrophilic polymeric additives may be discharged so as to deteriorate the long-term stability of the membrane.
Another method of producing a membrane for fouling resistance is to coat a hydrophilic material on the surface of a manufactured membrane. As the hydrophilic material, polydopamine, a representative material of a bio-inspired polymer, may be applied.